1. Field of the Invention
The present invention relates to a wrench, and more particularly to a wrench in which an upper jaw member is rotatably mounted on a lower jaw member and always urged to its gripping position relative to the lower jaw member.
2. Description of the Prior Art
A conventional wrench of such kind will be first hereinbelow described with reference to FIG. 1 in which is shown the conventional wrench wherein: an upper jaw member 31 is inserted into a guide hole provided in a lower jaw member 32 integral with a handle portion 33 of the wrench, and then mounted on the lower jaw member 32 through a pin 34 so as to be rotatable in directions designated by arrows in solid line and dotted line. In a rear portion of the upper jaw member 31 is formed a projection 35 a lower surface of which abuts against a front end of a spring 36 which is mounted on the handle portion 33 to always urge the upper jaw member 31 in a direction designated by the arrow in solid line, i.e., to its gripping position. When the wrench does not grip any article, the upper jaw member 31 is brought into a contact with a stop portion 37 of the lower jaw member 32 in its lower surface so that an opening distance 40 between both grip teeth 38, 39 of the upper and lower jaw members is held in minimum.
In gripping an article 41 with the use of the conventional wrench, firstly the upper jaw member 31 is swung in the direction designated by the arrow in dotted line by means of a user's fingers so that an opening portion 40 of the wrench is enlarged in its width to introduce the article 41 therein. After the article 41 is introduced into the opening 40 of the wrench, the upper jaw member 31 is released from the user's fingers so that the upper jaw member 31 is driven under the effect of a resilient force of the spring 36 to grip the article 41 in cooperation with the lower jaw member 32 between their grip teeth 38, 39.
However, it is hard to grip the article 41 in a steady manner with the use of such conventional wrench when the article 41 varies in size, because such article 41 abuts against the grip teeth 38, 39 in different positions depending upon its size. In addition to the above, the conventional wrench has another disadvantage in that it is hard to grip the article 41 a size of which is considerably smaller or larger than that of the article shown in FIG. 1 in diameter because the opening distance 40 of such wrench can not be varied over a wide range.